JP6965044B2 - Vibration type actuator control device, vibration type actuator control method, vibration type drive device and electronic equipment - Google Patents

Description

The present invention relates to a control device for a vibration type actuator, a control method for a vibration type actuator, a vibration type drive device, and an electronic device.

As a non-electromagnetically driven actuator, there is known a vibrating actuator in which a vibrating body and a driven body are brought into pressure contact with each other and the vibrating body and the driven body are relatively moved by vibration excited by the vibrating body. The vibrating body has, for example, a structure in which an electric-mechanical energy conversion element such as a piezoelectric element is bonded to an elastic body. In a vibrating actuator, a high-frequency vibration is generated in a vibrating body by applying an AC driving voltage to an electric-mechanical energy conversion element, and the generated vibration energy is used as a mechanical motion of relative movement between the vibrating body and the driven body. Take it out.

Various techniques for improving the starting performance of a driven object have been proposed in a device using a vibration type actuator. For example, in Patent Document 1, it is determined whether or not the actual speed reaches the reference speed when the amplitude of the voltage value output by the potential detection sensor provided in the piezoelectric element exceeds a predetermined value, and the determination result is obtained. Based on this, a control method for changing the rate of change of the drive frequency has been proposed. Further, Patent Document 2 proposes a control method for restricting frequency sweep when the voltage value output by the potential detection sensor provided in the piezoelectric element at the time of activation becomes a predetermined value or more. Further, since slippage may occur between the vibrating body and the driven body and the vibrating actuator may be worn, a technique for preventing such wear has been proposed, for example, in Patent Document 3. In the technique of Patent Document 3, the vibration speed of the driving force transmitting member is obtained from the driving command signal based on the relationship between the driving command signal and the vibration speed set in advance, while the position information (detection speed) of the stage is obtained. .. After that, the sliding amount of the driving force transmitting member and the stage, and the friction work are calculated based on the vibration speed and the position information (detection speed). Then, when the friction work exceeds a preset standard value, the control parameter used for feedback control to the ultrasonic motor is changed. Further, for example, in Patent Document 4, in the drive control of the vibration type actuator, the output of the drive frequency control circuit to which the output voltage of the electrode of the piezoelectric element is input is fed back to the oscillator, and the drive frequency of the vibration type actuator is controlled. NS.

Japanese Patent No. 4478407 Japanese Unexamined Patent Publication No. 04-140077 Japanese Unexamined Patent Publication No. 2003-324974 Japanese Unexamined Patent Publication No. 2000-278966

However, when it is necessary to suddenly accelerate or decelerate the driven object at high speed, even when the above-mentioned prior art is applied, it is caused by slippage that occurs on the frictional sliding surface between the vibrating body and the driven body. Therefore, the desired acceleration performance and deceleration performance may not be obtained.

An object of the present invention is to provide a technique capable of improving acceleration performance and deceleration performance when driving a vibrating actuator.

The control device for a vibrating actuator that relatively moves a vibrating body and a driven body according to the present invention is a case where the vibrating body is vibrated at a predetermined frequency by applying a predetermined driving voltage to the vibrating body. The vibration conversion means for obtaining the vibration conversion speed, which is the moving speed of the driven body when slip does not occur between the vibrating body and the driven body, and the vibrating body are defined as described above. when is vibrated at a frequency, wherein the detecting means that detect the actual moving speed is the actual moving speed of the driven member, the relative vibration conversion rate determined by said vibration converting means, said detecting means If the actual moving speed detected is smaller by, and having an a control means for reducing the vibration conversion rate.

According to the present invention, acceleration performance and deceleration performance can be improved when driving a vibrating actuator.

It is a block diagram which shows the schematic structure of the vibration type drive device which concerns on embodiment of this invention. It is the schematic sectional drawing of the vibration type actuator which comprises the vibration type drive device. It is sectional drawing of the digital single-lens reflex camera and the external perspective view of the main body part. It is a figure explaining the drive part which the control device which comprises the vibration type drive device has. It is a graph which shows the drive characteristic of the vibration type actuator by the conventional control method. It is a figure explaining the comparison calculation part which a control device has. It is a figure explaining the vibration control part which a control device has. It is a figure explaining the vibration control part which a control device has. It is a figure explaining the vibration control part which a control device has. It is a timing chart when the frequency is controlled based on the slip ratio. It is a timing chart when the pulse width is adjusted based on the slip ratio. It is a timing chart when the phase difference is adjusted based on the slip ratio. It is a flowchart of the control method of the vibration type actuator by a control device. It is a comparative example and an Example which shows the drive test result of the vibration type actuator. It is a circuit diagram which shows the structure of the current detection circuit for detecting the vibration state of the vibrating body in a drive part.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of a vibration type drive device 20 according to an embodiment of the present invention. The vibration type drive device 20 includes a vibration type actuator 23, a control device 21, and a position sensor 150. The position sensor 150 may be considered as a component of the control device 21. The control device 21 includes a command unit 110, a control amount determination unit 120, a slip control unit 130, and a drive unit 140. The command unit 110 includes a command value determination unit 101, a target position comparison unit 102, a position command generation unit 118, and a position detection unit 109. The control amount determination unit 120 includes a frequency control unit 103, a voltage control unit 104, and a phase difference control unit 105. The slip control unit 130 includes a vibration control unit 116, a comparison calculation unit 115, a vibration detection unit 112, and a speed detection unit 113. The drive unit 140 includes an AC signal generation unit 106 and a booster circuit 107. The vibrating actuator 23 has a vibrating body 6, a driven body 117, and a sensor phase 111.

The control device 21 has a CPU, a ROM, a RAM, an electronic component, and an electric component. The CPU expands the program stored in the ROM into the RAM, and the functions of the respective parts constituting the control device 21 are realized to vibrate. The drive of the mold actuator 23 is controlled. The control device 21 is not limited to such a configuration, and the operation is controlled by, for example, a dedicated processor such as an ASIC that realizes all or part of the processing of each part by a logic circuit, and a dedicated processor. It may be composed of an electric circuit. Further, each part constituting the control device 21 can be implemented by software (program) or by hardware, and may be implemented by a combination of software and hardware. In the present embodiment, the control device 21 corresponds to a vibration detecting means, a relative speed detecting means, a vibration controlling means, and a speed acquiring means.

First, a schematic configuration and a drive mode of the vibration type actuator 23 to be driven and controlled by the control device 21 will be described. FIG. 2A is a cross-sectional view showing a schematic configuration of the vibration type actuator 23. The vibrating actuator 23 taken up here is roughly an output shaft arranged coaxially with the rotating body by generating a circular or elliptical motion in the friction portion of the rod-shaped vibrating body and rotating the rotating body pressed against the friction portion. The rotation output can be taken out to the outside through.

The vibrating actuator 23 includes a support member 3, a friction member 4, a rotating body 5, a vibrating body 6, case-side bearings 7, 9, a pressure receiving member 8, an output shaft 10, a pressure spring 11, a flexible printed substrate 12, and a case. 13 and 14 are provided. The vibrating body 6 has an amplitude expanding member 1 (elastic body) and a piezoelectric element 2. Further, the friction member 4, the rotating body 5, the pressure receiving member 8, the output shaft 10, and the pressure spring 11 constitute a driven body 117.

The vibrating body 6 has a rod-shaped (cylindrical) structure in which a piezoelectric element 2, a flexible printed substrate 12, and a support member 3, which are electro-mechanical energy conversion elements, are sandwiched by two amplitude expanding members 1. Each of the two amplitude expanding members 1 has a structure in which a vibrating body friction portion, a constricted portion, and a holding portion are integrally formed. The flexible printed substrate 12 supplies power to the piezoelectric element 2. The support member 3 is sandwiched between the cases 13 and 14 forming the exterior of the vibrating actuator 23, whereby the vibrating body 6 is held at a predetermined position in the cases 13 and 14 by the support member 3. The output shaft 10 is inserted into the hole provided on the inner diameter side of the vibrating body 6. The output shaft 10 is press-fitted into the case-side bearings 7 and 9 provided in the cases 13 and 14, respectively, and is positioned, and the vibrating body 6 is also positioned with respect to the output shaft 10.

The rotating body 5 is in pressure contact with the friction portion of the vibrating body 6. When a plurality of AC voltages (two-phase drive voltages VA and VB, which will be described later) are supplied to the piezoelectric element 2, two bending vibrations are combined at both ends of the vibrating body 6 in the thrust direction to cause a swinging motion. Occurs. Due to this swinging motion, a circular or elliptical motion is generated on the friction sliding surfaces of the friction portions provided at both ends (ends in the axial direction) of the vibrating body 6. On the other hand, a stepped friction member 4 made of stainless steel and having a pipe-like shape, which is manufactured by press working, is joined to the rotating body 5 by adhesive, brazing or welding. The end face of the friction member 4 is pressed against the friction sliding surface of the vibrating body 6 by the pressure spring 11, and the reaction force by the pressure spring 11 is received by the two pressure receiving members 8. Therefore, the rotating body 5 is rotated by the friction member 4 being frictionally driven by the circular or elliptical motion generated on the friction sliding surface of the vibrating body 6 and rotating around the output shaft 10, and the rotational force of the rotating body 5 is reduced. It is transmitted to the output shaft 10 via the detent. At this time, since the pressure receiving member 8, the output shaft 10 and the detent are joined by an adhesive, the rotational force of the rotating body 5 is surely transmitted to the output shaft 10. Instead of the method using an adhesive, spot welding or brazing with a laser or the like may be used for joining the pressure receiving member 8, the output shaft 10, and the detent.

The piezoelectric element 2 is provided with a sensor phase 111 (see FIG. 1) having a structure in which a piezoelectric material is sandwiched between electrodes. When an AC voltage is applied to the piezoelectric element 2 to drive (vibrate) the piezoelectric element 2, an AC voltage is generated in the sensor phase 111. Therefore, the vibration state (vibration displacement) of the vibrating body 6 can be detected by monitoring the voltage value (hereinafter referred to as "S-phase voltage (vibration voltage)") and phase of the AC voltage output from the sensor phase 111. can. Even when the piezoelectric element 2 is not provided with the sensor phase 111, the vibration state of the vibrating body 6 can be detected by measuring the current (driving current) in the driving unit 140, which will be described later. The circuit configuration for measuring the drive current will be described later.

Although the details will be described later, the control device 21 applies the S-phase voltage output from the sensor phase 111 to the rotation speed (when no slip occurs between the vibrating body 6 and the driven body 117 (friction member 4). Convert to (rotational speed in steady state). Here, when the mechanical vibration displacement generated in the piezoelectric element 2 becomes large, the S-phase voltage becomes high. Therefore, when the monitored S-phase voltage is high, it corresponds to the case where the vibration displacement of the piezoelectric element 2 is large and the rotation speed in the steady state is high. In the present embodiment, the rotation speed in the steady state is hereinafter referred to as "vibration conversion speed (detection result)". Further, the position sensor 150 is attached to the output shaft 10 (or the connecting portion between the output shaft 10 and the object to be driven), and the output signal from the position sensor 150 is the actual rotation speed of the driven body 117 (hereinafter, “actual”). It is used to detect the rotation speed (relative speed, detection result) ") and the current position. The current position of the driven body 117 refers to the relative rotation angle of the driven body 117 with respect to the vibrating body 6 because the vibrating actuator 23 rotationally drives the driven body 117 in the present embodiment. The control device 21 is generated between the vibrating body 6 and the driven body 117 (friction member 4) based on the relationship between the steady rotation speed of the driven body 117 and the actual rotation speed of the driven body 117. Detect slipping. Then, the control device 21 operates a control amount for generating an AC voltage to be supplied to the piezoelectric element 2 so as to reduce this slip.

The vibrating actuator that can be driven by the control device 21 according to the present embodiment is not limited to the structure shown in FIG. 2A. FIG. 2B is a cross-sectional view showing a schematic configuration of a well-known vibration type actuator, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-211785. The vibrating actuator of FIG. 2B does not have an output shaft, and output to the outside is performed via a gear.

The vibrating actuator 23 can be used, for example, to drive a mirror, a shutter, a lens, or the like provided in an imaging device such as a digital single-lens reflex camera. As an example, a configuration in which the vibration type actuator 23 is applied to drive a quick return mirror of a digital single-lens reflex camera will be described.

FIG. 3A is an external perspective view of the main body 30 of the digital single-lens reflex camera. FIG. 3B is a cross-sectional view showing a schematic configuration of a digital single-lens reflex camera. An interchangeable lens 31 (lens lens barrel) is removable from the mount provided on the front surface of the main body 30. A mirror box 32 for guiding a luminous flux that has passed through the interchangeable lens 31 is arranged inside the main body 30, and a main mirror 33 (quick return mirror) is arranged inside the mirror box 32. An image sensor 36 such as a CCD sensor or a CMOS sensor is arranged on the photographing optical axis of the interchangeable lens 31 inside the main body 30. The luminous flux that has passed through the interchangeable lens 31 is imaged on the image pickup surface of the image pickup element 36. The optical image formed on the image pickup surface is converted into an electric signal by photoelectric conversion by the image pickup device 36, and then converted into image data by a well-known technique by an image processing circuit (not shown).

When the photographer observes the subject image from the finder eyepiece window 34, the main mirror 33 arranged inside the mirror box 32 is provided, for example, on the shooting optical axis in order to guide the shooting light flux to the finder eyepiece window 34. It is held in the first position at an angle of 45 degrees with respect to it. On the other hand, when the photographer presses the shutter button to take a picture, the photographer is held at a second position retracted from the photographed luminous flux in order to guide the photographed luminous flux to the image sensor 36. In order to increase the frame speed at the time of shooting, it is necessary to switch the main mirror 33 between the first position and the second position at high speed.

The drive shaft of the main mirror 33 is connected to the output shaft 10 of the vibrating actuator 23, and the rotational driving force of the vibrating actuator 23 reciprocates the main mirror 33 between the first position and the second position. .. At that time, the position and rotation speed of the main mirror 33 are controlled by adjusting the rotation speed and rotation angle of the output shaft 10 by adjusting the frequency, voltage value, and phase difference of the AC voltage applied to the piezoelectric element 2. Can be done by. The control device 21 controls the drive of the vibrating actuator 23 so that the main mirror 33 accelerates from a stationary state to a predetermined speed, moves at a constant speed, then decelerates as it approaches the target position and stops at the target position. .. The drive shaft of the main mirror 33 may be connected to the vibration type actuator 23 via a gear, a link mechanism, or the like.

Next, the configuration and operation of the control device 21 will be described in detail. In the following description, "driving the vibrating actuator 23" means controlling changes in the actual rotation speed and position (rotation angle) of the driven body 117 by controlling two bending vibrations excited by the vibrating body 6. Refers to doing. In the vibrating actuator 23, as described above, the vibrating body 6 is fixed and the driven body 117 rotates. Therefore, the actual rotation speed and position (rotation angle) of the driven body 117 are synonymous with the rotation speed and position (rotation angle) of the driven body 117 relative to the vibrating body 6, respectively.

The position sensor 150 included in the vibration type drive device 20 is, for example, an optical rotary encoder, which is a reflective or transmissive scale formed on a lattice disk fixed to an output shaft 10 at a predetermined pitch in the circumferential direction. It is read by an optical sensor. The output signal from the position sensor 150 is transmitted to the speed detection unit 113 of the slip control unit 130. On the other hand, the S-phase voltage output from the sensor phase 111 is transmitted to the vibration detection unit 112 of the slip control unit 130.

In the slip control unit 130, the vibration detection unit 112 is based on the S-phase voltage output from the sensor phase 111, and the rotation speed of the driven body 117 when no slip occurs between the vibrating body 6 and the friction member 4. (Rotation speed in steady state) is calculated. Further, the speed detection unit 113 detects the actual rotation speed of the driven body 117 based on the output signal from the position sensor 150. The comparison calculation unit 115 is based on the steady-state rotation speed of the driven body 117 detected by the vibration detection unit 112 and the actual rotation speed of the driven body 117 detected by the speed detection unit 113, and the vibrating body 6 and the friction member 4 The slip rate (details will be described later) that occurs between and is calculated. In the slip control unit 130, the vibration control unit 116 operates and generates at least one of the frequency, voltage, and phase difference of the AC voltage supplied to the piezoelectric element 2 based on the slip ratio calculated by the comparison calculation unit 115. The operation signal is transmitted to the control amount determination unit 120.

The command unit 110 is composed of various electronic devices and electrical components such as a CPU, PLD (including ASIC), ROM, RAM, and A / D converter, and is information for controlling the drive of the vibration type actuator 23. Generate a signal containing. Specifically, the position command generation unit 118 calculates the target position for each control sampling (every time). The output signal from the position sensor 150 is also transmitted to the position detection unit 109 of the command unit 110, and the position detection unit 109 detects the current position of the driven body 117 based on the output signal from the position sensor 150. The target position comparison unit 102 sequentially calculates the deviation between the current position calculated by the position detection unit 109 and the target position generated by the position command generation unit 118, and uses the calculated deviation as the command value determination unit 101 and the control amount determination unit. Output to 120. The command value determination unit 101 outputs a speed command, a voltage command, and a drive direction command having information on each of the speed, voltage, and drive direction to the control amount determination unit 120 based on the deviation acquired from the target position comparison unit 102. The command unit 110 may drive while maintaining the initial start-up value, and may perform open drive in which the power is turned off and the drive of the vibrating body 6 is stopped when the driven body 117 reaches the target position. Then, the feedback calculation by the PID compensator or the like may be performed using the deviation.

The speed command, voltage command, and drive direction command determined by the command value determination unit 101 are transmitted to the frequency control unit 103, the voltage control unit 104, and the phase difference control unit 105 of the control amount determination unit 120, respectively. In the control amount determination unit 120, the frequency control unit 103, the voltage control unit 104, and the phase difference control unit 105, respectively, based on the operation signal acquired from the slip control unit 130 and the command signal acquired from the command unit 110, the frequency, voltage, and Determines the amount of phase difference control. The frequency, voltage, and phase difference control amounts determined by the control amount determination unit 120 are transmitted to the AC signal generation unit 106 of the drive unit 140.

The AC signal generation unit 106 is composed of, for example, a CPU, a function generator, a switching circuit, etc., and determines the frequency, pulse width, and phase difference of the AC pulse signal for generating the AC voltage to be supplied to the vibration type actuator 23. adjust. In the following description, the AC voltage supplied from the drive unit 140 to the piezoelectric element 2 will be referred to as drive voltages VA and VB.

The AC signal generation unit 106 generates a square wave two-phase AC signal based on each control amount of frequency, pulse width, and phase difference input from the control amount determination unit 120, and generates the generated two-phase AC signal. Output to the booster circuit 107. The booster circuit 107 boosts the two-phase AC signal acquired from the AC signal generation unit 106 to a predetermined voltage value to generate drive voltages VA and VB, and uses the generated drive voltages VA and VB as the piezoelectric element of the vibrating body 6. Apply to 2. As a result, the driven body 117 is frictionally driven by the vibration of the predetermined vibration mode excited by the vibrating body 6, and the driven body 117 can be rotated in a predetermined direction at a predetermined speed.

As described above, since the actual rotation speed and the current position of the driven body 117 can be obtained from the output from the position sensor 150, the output signal from the position sensor 150 is fed back to the slip control unit 130 and commanded. It is fed back to the unit 110. Further, the S-phase voltage output from the sensor phase 111 is fed back to the slip control unit 130.

Here, the configuration of the drive unit 140 will be described. FIG. 4A is a block diagram showing a schematic configuration of the drive unit 140. The AC signal generation unit 106 includes a pulse signal generation unit 165 and a switching circuit 160. The booster circuit 107 has a coil 162 and a transformer 163, but may be composed of only the coil 162 or only the transformer 163. Since the configuration of the portion that generates the drive voltage VA and the portion that generates the drive voltage VB are the same, only the pulse signal generation unit and the switching circuit used for generating the drive voltage VA will be described.

The pulse signal generation unit 165 is a phase A pulse signal whose phase is 180 degrees out of phase with the rectangular A-phase pulse signal corresponding to each control amount of frequency, pulse width, and phase difference from the control amount determination unit 120. Generates an inverting pulse signal. FIG. 4B is a diagram showing a pulse signal generated by the pulse signal generation unit 165. The A-phase pulse signal and the A-phase inversion pulse signal generated by the pulse signal generation unit 165 are input to the switching circuit 160. The switching circuit 160 switches the DC voltage supplied from the power supply 161 at the timing of the input pulse signal to generate a square wave AC signal. When the pulse width of the pulse signal generated by the pulse signal generation unit 165 is represented by the duty ratio, the pulse width of the AC signal generated by the AC signal generation unit 106 is also represented by the same duty ratio.

The AC signal output from the AC signal generation unit 106 is input to the booster circuit 107 and boosted to a predetermined voltage value to be converted into a sine wave drive voltage VA, and one electrode (A phase) of the piezoelectric element 2 is converted. ) Is applied. The B-phase pulse signal used to generate the drive voltage VB applied to the other electrode (B-phase) of the piezoelectric element 2 has a phase difference output from the control amount determining unit 120 with respect to the A-phase pulse signal. It is generated so as to have a predetermined phase difference based on the information of. Further, the B-phase inversion pulse signal is generated so as to be 180 degrees out of phase with the B-phase pulse signal. The drive voltage VB of the sine wave is generated in the same manner as the drive voltage VA.

Further, as described above, when the sensor phase 111 is not provided in the piezoelectric element 2, the drive unit 140 is provided with a current detection circuit for detecting the drive current. For example, the current detection circuit 164 shown in FIG. 15A detects the magnitude of the current flowing through the resistor 169 provided between the power supply 161 and the switching circuit 160. When the drive voltages VA and VB are applied to the piezoelectric element 2 to drive the piezoelectric element 2, the current flowing through the current detection circuit 164 including the resistor 169 increases according to the magnitude of the mechanical vibration displacement generated in the piezoelectric element 2. .. Therefore, the vibration state (vibration displacement) of the vibrating body 6 can be indirectly detected by detecting the current value flowing from the power supply 161 to the resistor 169. The current value is amplified by using a differential amplifier 166 or the like, further AD-converted, and output to the control circuit. In this embodiment, the current value detected by the current detection circuit 164 is defined as "drive current". Further, for example, in the current detection circuit 167 shown in FIG. 15B, the magnitude of the current flowing through the resistor 168 provided at one end of the booster circuit 107 is detected. When the drive voltages VA and VB are applied to the piezoelectric element 2 to drive the piezoelectric element 2, the current flowing through the boosting coil (transformer 163) increases according to the magnitude of the mechanical vibration displacement generated in the piezoelectric element 2. Therefore, the vibration state (vibration displacement) of the vibrating body 6 can be indirectly detected by detecting the current value (driving current) flowing through the resistor 168 connected to the transformer 163. The current detection resistor may be provided on the secondary side of the transformer 163. Further, as long as the current flowing through the current detection circuit 167 can be detected, the place where the resistor is provided does not matter. The detected drive current is amplified by using a differential amplifier 166 or the like, further AD-converted, and output to the control circuit. In the control circuit, the drive current is converted into the magnitude of the vibration displacement of the piezoelectric element 2 and, by extension, the rotation speed in the steady state, similarly to the S-phase voltage.

Next, a method of controlling the vibration type actuator 23 by the control device 21 will be described. First, the sliding of the friction sliding surface between the vibrating body 6 and the friction member 4 will be described. FIG. 5 is a graph showing the relationship between the rotational speed of the driven body 117 and the S-phase voltage obtained from the sensor phase 111 when the vibrating actuator 23 is driven by a conventional control method. The rotation speed of the driven body 117 is the actual rotation speed of the driven body 117 (output shaft 10) measured by the position sensor 150. Further, in the graph of FIG. 5, time is taken on the horizontal axis, and S-phase voltage (Vp−p) and rotation speed (rpm) are taken on the vertical axis, and the S-phase voltage and rotation in 30 ms to 40 ms until a steady state is reached. The ranges of the two vertical axes are aligned so that they match the speed.

There is a difference between the S-phase voltage and the rotation speed of the driven body 117 in the acceleration region and the deceleration region of the driven body 117, and this difference is particularly remarkable in the acceleration region. This is because, although the vibration amplitude of the vibrating body 6 is sufficiently large, the frictional sliding surface between the vibrating body 6 and the friction member 4 slips, and the rotation speed of the driven body 117 does not increase. Is. When the friction sliding surface between the vibrating body 6 and the friction member 4 slips, the efficiency is lowered and the electric power is excessively consumed, which causes a problem that the peak electric power becomes large. Therefore, the control device 21 according to the present embodiment detects slippage on the frictional sliding surface between the vibrating body 6 and the friction member 4, and controls the drive of the vibration type actuator 23 so that the occurrence of slippage is suppressed. do.

FIG. 6A is a block diagram showing the configuration of the comparison calculation unit 115 included in the slip control unit 130 of the control device 21. The comparison calculation unit 115 calculates the slip ratio as a value representing the slip on the friction sliding surface between the vibrating body 6 and the friction member 4 based on the output values from each of the speed detection unit 113 and the vibration detection unit 112. .. The comparison calculation unit 115 has a divider 201. In the present embodiment, the divider 201 divides the actual rotation speed by the vibration conversion speed. The comparison calculation unit 115 subtracts the value obtained by dividing the actual rotation speed by the vibration conversion speed from 1, and calculates the slip ratio by "slip rate = 1- (actual rotation speed / vibration conversion speed)". The vibration conversion speed, which is an output signal from the vibration detection unit 112, corresponds to the rotation speed in a steady state corresponding to the voltage value of the S-phase voltage representing the vibration state of the vibrating body 6. That is, the vibration conversion speed is the rotation speed of the driven body 117 that does not consider slippage on the friction sliding surface between the vibrating body 6 and the friction member 4. Since the actual rotation speed of the driven body 117 is detected by the speed detection unit 113 based on the output signal from the position sensor 150, the slip ratio during acceleration / deceleration can be detected by obtaining the ratio of the two. For example, if the actual rotation speed and the vibration conversion speed are equal, the slip ratio is 0%, and it can be said that the driving state is in a good state in which slip does not occur. On the contrary, when the actual rotation speed is zero (0), the slip ratio is 100%, and it can be said that the vibrating body 6 cannot transmit the driving force to the driven body 117.

FIG. 6B is a diagram illustrating an output from the vibration detection unit 112. The vibration conversion speed is calculated using an approximate expression based on the S phase voltage input from the sensor phase 111, and is calculated as, for example, "vibration conversion speed N1 when the S phase voltage Vs". As described above, when the S-phase voltage is high, the vibration displacement of the piezoelectric element 2 is large and the vibration conversion speed is high. That is, since the S-phase voltage and the vibration conversion speed are generally in a proportional relationship, a linear function as shown in FIG. 6B can be used as an approximate expression. A non-linear approximation formula or a look-up table (LUT) may be used as the relational expression between the S-phase voltage and the vibration conversion speed, and these relational expressions are calculated from the measurement data acquired in advance. Here, as a method of calculating the vibration conversion speed, the relationship between the parameters (drive command signal) such as the frequency and voltage value of the drive voltage for driving the vibrating body and the vibration conversion speed is set in advance, and the relationship is set. A method of calculating the vibration conversion speed based on this is also conceivable. However, the relationship between the drive voltage parameter and the vibration conversion speed is different between a stable steady state in which the driven body is not accelerated or decelerated and a transient state in which the driven body is accelerated or decelerated and the friction state is rapidly converted. Therefore, when calculating the vibration conversion speed based on the drive voltage parameter, it may not be possible to obtain an accurate vibration conversion speed depending on the frictional state. On the other hand, in the present embodiment, the vibration conversion speed is calculated based on the S-phase voltage (vibration voltage) generated in response to the vibration of the vibrating body 6, which is different from the driving voltage. Since the S-phase voltage is determined only by the vibration of the vibrating body 6, the present embodiment has an advantage that an accurate vibration conversion speed can be obtained regardless of the frictional state. Further, when the drive current is detected by using the current detection circuits 164 and 167 shown in FIG. 15, since the drive current is determined only by the vibration displacement of the piezoelectric element 2, an accurate vibration conversion speed can be obtained regardless of the friction state. It has the advantage of being able to be used. In the present embodiment, as described above, the S-phase voltage is converted into the rotation speed and compared with the actual rotation speed, but the actual rotation speed is converted into the voltage value corresponding to the S-phase voltage and the S-phase voltage is obtained. May be compared with.

Subsequently, the control amount generated by the vibration control unit 116 based on the slip ratio calculated by the comparison calculation unit 115 will be described. 7, 8 and 9 are diagrams for explaining the configuration of the vibration control unit 116, respectively. The vibration control unit 116 performs a calculation using the slip ratio acquired from the comparison calculation unit 115 as an input, thereby generating the drive voltages VA and VB for driving the vibration type actuator 23, and the frequency, pulse width, and phase difference. Is output to the control amount determination unit 120. The vibration control unit 116 includes a frequency calculation unit 310, a pulse width calculation unit 410, and a phase difference calculation unit 510 in order to calculate these control quantities. FIG. 7 is a diagram for explaining the frequency calculation unit 310, FIG. 8 is a diagram for explaining the pulse width calculation unit 410, FIG. 9 is a diagram for explaining the phase difference calculation unit 510, and each figure will be described below. do.

FIG. 7A is a block diagram showing the configuration of the frequency calculation unit 310. The frequency calculation unit 310 controls the frequency based on the slip ratio. The slip ratio calculated by the comparison calculation unit 115 is input to the limiter 301, and is output in a value in the range of 0 to 1 from the limiter 301. In the multiplier 302, the output value from the limiter 301 and the frequency change amount Δf (= f1-f0) are multiplied. The frequency change amount Δf is a preset value, and the rotation speed of the driven body 117 can be controlled according to the slip by manipulating the frequency in the range of the initial frequency f0 to the frequency f1. FIG. 7B is a diagram showing the frequency change amount Δf output with respect to the slip ratio. The relationship between the slip ratio and the frequency change amount Δf may be the linear characteristic shown in Example 1 or the non-linear characteristic shown in Example 2. The adder 304 adds the frequency change amount Δf to the initial frequency f0. That is, the frequency control amount falls within the range from the initial frequency f0 to the frequency f1, and is output to the frequency control unit 103. Here, when the frequency for generating the drive voltages VA and VB becomes high, the vibration (rotational speed) of the vibrating body 6 decreases.

By the way, for example, when a vehicle tire starts to slip on a frozen road surface, the slip is eliminated by reducing the rotation speed of the tire. In the present embodiment, as shown in FIG. 7B, this principle is used, and when the slip ratio increases, the frequency change amount Δf is increased to increase the frequency, thereby causing the vibrating body 6 to vibrate ( Rotation speed) is reduced. As a result, the slip ratio is reduced and the transmission efficiency is improved. Further, when the slip ratio is reduced, the frequency change amount Δf is reduced to suppress the frequency increase, that is, to reduce the frequency change, thereby increasing the vibration (rotational speed) of the vibrating body 6 and improving the power. Further, the S-phase voltage can be detected at the time of acceleration or deceleration of the vibrating body 6 and the driven body 117. That is, the S-phase voltage can be detected even when the vibrating body 6 and the driven body 117 are in a transient state. At this time, the S-phase voltage is sequentially detected, the slip ratio is calculated based on the S-phase voltage, and as described above, the frequency for generating the drive voltages VA and VB is controlled to be transient. The efficiency of motor performance can be improved. In this case, the S-phase voltage is detected and the slip ratio is calculated for each predetermined sampling cycle during driving of the driven body 117 or for each cycle similar thereto, and the parameters of the drive voltages VA and VB are calculated based on the slip ratio. May be operated. Thereby, the efficiency of the motor performance can be appropriately improved.

In the control of a normal vibration type actuator, the PID gain of the feedback control is adjusted for each drive sequence consisting of acceleration, steady speed, and deceleration operations, or the slip ratio during driving is averaged and compared with the threshold value to compare the PID gain. Determine whether to change. That is, while the control unit of the drive voltage is the drive sequence unit, in the present embodiment, even when the vibrating body 6 or the driven body 117 is accelerating or decelerating, the driving voltages VA and VB are sequentially generated. You can manipulate the parameters. Therefore, in the present embodiment, more efficient driving can be realized as compared with the conventional case.

FIG. 8A is a block diagram showing the configuration of the pulse width calculation unit 410. The pulse width calculation unit 410 controls the voltage by manipulating the pulse width based on the slip ratio. The slip ratio calculated by the comparison calculation unit 115 is input to the limiter 401, and is output in a value in the range of 0 to 1 from the limiter 401. The LUT 402 obtains the pulse width based on the output value from the limiter 401 and outputs the pulse width to the voltage control unit 104. FIG. 8B is a diagram showing an output value of the pulse width with respect to the slip ratio. Basically, the pulse width is output so as to decrease as the slip ratio increases. For example, when the slip ratio is 0.5 or less, the pulse width is set to 50%, and when the slip ratio is 1.0, the pulse width is set. It is desirable to set it to 10%. This is because the pulse width for obtaining the minimum voltage required for starting the vibrating actuator 23 is 10%, and if the pulse width is further reduced, the friction sliding surface between the vibrating body 6 and the friction member 4 This is because the friction state changes significantly from the dynamic friction to the static friction state.

FIG. 9A is a block diagram showing the configuration of the phase difference calculation unit 510. The phase difference calculation unit 510 controls the phase difference based on the slip ratio. The slip ratio calculated by the comparison calculation unit 115 is input to the limiter 501, and is output in a value in the range of 0 to 1 from the limiter 501. The LUT 502 obtains the phase difference based on the output value from the limiter 501, and outputs the phase difference to the phase difference control unit 105. FIG. 9B is a diagram showing an output value of the phase difference with respect to the slip ratio. Basically, the phase difference is output so as to decrease as the slip ratio increases. However, in consideration of the non-linear characteristics of the S-phase voltage with respect to the phase difference, it is desirable to set the slip ratio to 1.0 and the phase difference to 20 degrees, for example.

Next, a timing chart relating to drive control of the vibration type actuator 23 by the control device 21 will be described. FIG. 10 is a timing chart when the frequency is controlled based on the slip ratio. FIG. 10A shows changes over time in the current position, actual rotation speed, slip ratio, and drive frequency (frequency of drive voltages VA and VB) of the driven body 117. The vibration type actuator 23 is controlled so that the drive is started at time t0, reaches the target speed at time t1, decelerates at time t2, and reaches the target position (target rotation angle) at time t3. Focusing on the acceleration period of time t0 to t1 and the deceleration period of time t2 to t3, the vibration conversion speed of the broken line and the actual rotation speed of the solid line differ depending on the slip of the friction sliding surface between the vibrating body 6 and the friction member 4. Occurs. As a result, as described above, the comparison calculation unit 115 calculates the slip ratio, and the frequency calculation unit 310 of the vibration control unit 116 operates the drive frequency so that the slip ratio becomes small. FIG. 10B shows the relationship between the S-phase voltage output from the sensor phase 111 and the operated frequency. When the drive frequency is operated to the frequency f1 side (the drive frequency is increased), the vibration of the vibrating body 6 is reduced, the vibration conversion speed is also reduced, and the S-phase voltage is reduced. Here, according to the above-mentioned calculation formula of the slip ratio, a state in which the slip ratio is large is nothing but a state in which the vibration conversion speed is excessive. Therefore, in the present embodiment, when the slip ratio is large, the drive frequency is operated to the frequency f1 side to reduce the vibration conversion speed (reduce the vibration of the vibrating body 6) and reduce the slip ratio. That is, in the present embodiment, when the slip ratio is large, the vibration (rotational speed) of the vibrating body 6 is reduced by increasing the frequency, while when the slip ratio is small, the frequency of the vibrating body 6 is reduced. Increase vibration (rotational speed). Further, even when the vibrating body 6 or the driven body 117 is accelerating or decelerating, the S-phase voltage is sequentially detected to calculate the slip ratio, and the driving voltages VA and VB are generated based on the slip ratio. Change the frequency of. This makes it possible to improve the efficiency of transient motor performance. Further, the S-phase voltage is detected and the slip ratio is calculated for each predetermined sampling cycle during driving of the driven body 117 or for each cycle similar thereto, and the parameters of the drive voltages VA and VB are set based on the slip ratio. Manipulate. As a result, efficient driving with reduced slippage can be realized.

FIG. 11 is a timing chart in the case of controlling the voltage values of the drive voltages VA and VB by adjusting the pulse width based on the slip ratio. FIG. 11A shows changes over time in the current position, actual rotation speed, slip ratio, and pulse width of the driven body 117. Since the current position, the actual rotation speed, and the slip ratio of the driven body 117 shown in FIG. 11A are the same as those in FIG. 10A, the description thereof will be omitted. When the slip ratio is calculated by the comparison calculation unit 115, the pulse width calculation unit 410 of the vibration control unit 116 operates the pulse width so that the slip ratio becomes small. FIG. 11B shows the relationship between the S-phase voltage output from the sensor phase 111 and the operated pulse width. When the pulse width is operated to the 0% side, the vibration of the vibrating body 6 is reduced, the vibration conversion speed is also reduced, and the S-phase voltage is reduced. Therefore, when the vibration conversion speed becomes excessive and the slip ratio is large, the vibration conversion speed can be reduced (the S-phase voltage is reduced) and the slip ratio can be reduced by operating the pulse width to the 0% side. .. However, as described above, it is desirable that the pulse width is not less than 10%.

FIG. 12 is a timing chart when the phase difference is controlled based on the slip ratio. FIG. 12A shows changes over time in the current position, actual rotation speed, slip ratio, and phase difference of the driven body 117. Since the current position, the actual rotation speed, and the slip ratio of the driven body 117 shown in FIG. 12A are the same as those in FIG. 10A, the description thereof will be omitted. When the slip ratio is calculated by the comparison calculation unit 115, the phase difference calculation unit 510 of the vibration control unit 116 operates the phase difference so that the slip ratio becomes small. The phase difference at the time of starting the vibration type actuator 23 is not limited to 90 degrees, and may be 80 degrees or 100 degrees. FIG. 12B shows the relationship between the S-phase voltage output from the sensor phase 111 and the manipulated phase difference. When the phase difference is operated to the 0 degree side, the vibration that moves the driven body 117 in the forward direction of the driving direction becomes small, and the vibration conversion speed also becomes small. At this time, the S-phase voltage indicating the vibration becomes smaller. Therefore, when the vibration conversion speed becomes excessive and the slip ratio is large, the vibration conversion speed can be reduced (the S-phase voltage is reduced) and the slip ratio can be reduced by operating the phase difference to the 0 degree side. ..

The vibration control unit 116 may use all the calculation units of the frequency calculation unit 310, the pulse width calculation unit 410, and the phase difference calculation unit 510, or may use at least one calculation unit. May be good. That is, the slip control unit 130 may control any one of the frequency, the pulse width, and the phase difference based on the slip ratio, or may control by combining these.

FIG. 13 is a flowchart illustrating a method of controlling the vibration type actuator 23 by the control device 21. As described above, the control device 21 has a CPU, a ROM, a RAM, and the like, and in each process of the flowchart of FIG. 13, the CPU expands the program stored in the ROM into the RAM, and each part of the control device 21 It is realized by controlling the operation.

In step S1, a target position (target rotation angle) is set, and a command value having information on speed, drive voltage, and drive direction is output from the command unit 110. In step S2, start-up initial values are set in the frequency control unit 103, the voltage control unit 104, and the phase difference control unit 105 based on the command value. In step S3, drive voltages VA and VB are applied from the drive unit 140 to the vibrating actuator 23 (piezoelectric element 2), and the driven body 117 is started to be driven. In step S4, the S-phase voltage output from the sensor phase 111 provided in the vibrating actuator 23 is detected, and the actual rotation speed and the current position of the driven body 117 are determined based on the output signal from the position sensor 150. Detected. In step S5, the slip rate is calculated by the slip control unit 130 from the vibration conversion speed and the actual rotation speed calculated based on the information acquired in step S4, and the control amount is adjusted based on the calculated slip rate. In step S6, the command unit 110 compares the target position with the current position, and determines whether or not the target position has been reached. If it is determined that the current position has not reached the target position (NO in S6), the process is returned to step S4, and if it is determined that the current position has reached the target position (YES in S6), the process is performed. The process proceeds to step S7. In step S7, the outputs of the drive voltages VA and VB from the drive unit 140 are stopped, and the driven body 117 is stopped.

FIG. 14 is a diagram showing test results when the vibration type actuator 23 is driven by each of the control device 21 and the conventional control device. The drive conditions of the vibration type actuator 23 are 18 V for the power supply 161, 37.4 kHz for the initial frequency f0, 50% for the pulse width, and 90 degrees for the phase difference. When the test result shown in FIG. 14 was obtained, the S-phase voltage was detected to calculate the vibration conversion speed, but the drive current was detected to calculate the vibration conversion speed, and the test result as shown in FIG. May be obtained.

14 (a) to 14 (c) are diagrams showing test results according to a comparative example, and show changes over time in actual rotation speed, slip ratio, and power consumption when a conventional control device is used. In drive control using a conventional control device, the frequency, pulse width, and phase difference are fixed at initial values. In the conventional control method, since slippage occurs on the friction sliding surface between the vibrating body 6 and the friction member 4 during the acceleration period, the vibration conversion speed shown by the broken line and the actual rotation speed shown by the solid line are It can be seen that the difference is large. At this time, the slip ratio calculated by the comparison calculation unit 115 is 56% at the maximum, and as a result, the peak value of the power consumption reaches 8.3 W.

On the other hand, FIGS. 14 (d) to 14 (f) are diagrams showing the test results according to the examples, and show the changes over time in the actual rotation speed, slip rate, and power consumption when the control device 21 is used. In the drive control by the control device 21, the frequency calculation unit 310 controls the frequency based on the slip ratio by the slip control unit 130, but the pulse width and the phase difference are fixed at the initial values. Further, the frequency change amount Δf based on the slip ratio was set to 400 Hz, and the frequency was adjusted so as to change linearly in the range of 37.4 kHz to 37.8 kHz. As a result, it was confirmed that the slip ratio calculated by the comparison calculation unit 115 was reduced to 17% at the maximum, and the peak value of power consumption was also reduced to 5 W.

As described above, in the present embodiment, the control device 21 controls the drive of the vibrating actuator 23 so that the slip ratio on the friction sliding surface between the vibrating body 6 and the friction member 4 is reduced. As a result, transient slippage on the frictional sliding surface between the vibrating body 6 and the friction member 4 can be reduced, driving efficiency can be improved, and power consumption can be reduced. On the other hand, when acceleration performance is more important than power saving, by supplying the power required for conventional control, steeper acceleration and deceleration can be performed, and start-up performance can be improved. That is, it is possible to control the acceleration performance, the deceleration performance, and the power consumption in a balanced manner according to the application of the vibration type actuator 23.

Although the present invention has been described in detail based on the preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various embodiments within the scope of the gist of the present invention are also included in the present invention. Included in the invention. For example, the slip ratio as a value (comparison result) representing the slip between the vibrating body 6 and the friction member 4 was calculated by "slip ratio = 1- (actual rotation speed / vibration conversion speed)", but it is actually calculated from the vibration conversion speed. The difference obtained by subtracting the rotation speed may be used as a value (comparison result) representing the slip between the vibrating body 6 and the friction member 4. In this case, if the difference value is zero, slipping does not occur, and the degree of slipping increases as the absolute value of the difference value increases. In this case, the limiters 301, 401, 501 provided in each of the frequency calculation unit 310, the pulse width calculation unit 410, and the phase difference calculation unit 510 should be set with an upper limit value based on the maximum value of the experimentally obtained difference value. Just do it.

Further, the vibration type actuator whose drive can be controlled by the control device 21 is not limited to the structure shown in FIGS. 2 (a) and 2 (b). For example, a linear drive type vibrating actuator that applies a frictional driving force to a driven body that is in pressure contact with the tip of the protrusion by causing an elliptical motion at the tip of the protrusion provided on the plate-shaped vibrating body. Also, the present invention can be applied. In addition, it can also be used as an annular vibrating actuator that rotates an annular driven body by bringing an annular driven body into pressure contact with the annular vibrating body and exciting a traveling wave traveling in the circumferential direction to the vibrating body. , The present invention can be applied. When the control device 21 is applied to a linear drive type vibrating actuator, a linear encoder or the like is used as a position sensor, and the relative speed when the vibrating body and the driven body move linearly in a predetermined direction and The configuration may be such that the relative position is detected.

The application example of the vibration type drive device 20 is not limited to the mirror drive of the digital single-lens reflex camera described with reference to FIG. For example, by converting the rotation of the output shaft 10 of the vibrating actuator 23 into a linear movement via a gear or the like, a mechanism for moving the zoom lens or focus lens of the digital single-lens reflex camera in the direction of the shooting optical axis is constructed. be able to. Further, the vibration type drive device 20 can be used as a motor provided at a node of an articulated robot, for example, and is an electronic device including other parts that need to be positioned by driving a vibration type actuator. It can be widely applied to.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors of the computer of the system or device reads the program. It can also be realized by the processing to be executed. The present invention can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

2 Piezoelectric element 4 Friction member 6 Vibration body 20 Vibration type drive device 21 Control device 23 Vibration type actuator 110 Command unit 111 Sensor phase 116 Vibration control unit 117 Driven body 120 Control amount determination unit 130 Slip control unit 140 Drive unit 150 Position sensor 310 Frequency calculation unit 410 Pulse width calculation unit 510 Phase difference calculation unit

Claims (19)

A control device for a vibrating actuator that relatively moves the vibrating body and the driven body.
The case where the vibrating body is vibrated at a predetermined frequency by applying a predetermined driving voltage to the vibrating body, and slip does not occur between the vibrating body and the driven body. A vibration conversion means for obtaining the vibration conversion speed, which is the moving speed of the driven body, and
A detecting means that detect the actual moving speed which is the case where the vibrator is vibrated at a predetermined frequency, the actual moving speed of the driven body,
And characterized in that it has the relative vibration conversion rate determined by said vibration converting means, if the actual moving speed detected by said detecting means is small, and the control means for reducing the vibration conversion rate, the Control device. It has a comparison means for obtaining a value of a ratio of the actual moving speed to the vibration conversion speed.
The control means
The control device according to claim 1, wherein the vibration conversion speed is reduced as the value of the ratio obtained by the comparison means decreases. Before SL control means, based on the value representing the slip occurring between the vibrator and the driven member, which has been calculated based on the value of the ratio, and controlling the vibration state of the vibrating body The control device according to claim 2. The control device according to claim 3, wherein the control means obtains a value obtained by subtracting the value of the ratio from 1 as a value representing the slip. It has a comparison means for obtaining the difference between the vibration conversion speed and the actual movement speed.
The control means
The control device according to claim 1, wherein the vibration conversion speed is reduced as the difference obtained by the comparison means increases. 5. The control means according to claim 5, wherein the control means controls the vibration state of the vibrating body based on a value representing the slip generated between the vibrating body and the driven body obtained from the difference. Control device. Before SL control unit, every predetermined sampling period, obtains a value representing the slip, and based on the value representing the slip, said detecting means and the relative vibration in terms speed determined by the vibration converting means The control device according to any one of claims 3, 4 and 6 , characterized in that the vibration conversion speed is reduced when the actual moving speed detected by is small. The control device according to any one of claims 1 to 7 , further comprising a speed acquisition means for acquiring the vibration conversion speed. The vibrating body has an electro-mechanical energy conversion element.
The electric-mechanical energy conversion element has a sensor phase that outputs a vibration voltage generated in response to the vibration of the vibrating body.
The control device according to any one of claims 1 to 8, wherein the vibration conversion means obtains the vibration conversion speed from the magnitude of the vibration voltage output from the sensor phase. Further having a current detection circuit for outputting the drive current,
The control device according to claim 1, wherein the vibration conversion means obtains the vibration conversion speed from the magnitude of a drive current generated in response to the vibration of the vibrating body output from the current detection circuit. The control device according to any one of claims 1 to 10, wherein the control means reduces the vibration conversion speed by increasing the drive frequency for generating the drive voltage. The control device according to any one of claims 1 to 11, wherein the control means reduces the vibration conversion speed by reducing the pulse width for generating the drive voltage. The control device according to any one of claims 1 to 12, wherein the control means reduces the vibration conversion speed by reducing the phase difference for generating the drive voltage. The shape of the driven body is an annular shape, and the driven body has an annular shape.
The control device according to any one of claims 1 to 13, wherein the actual moving speed is the actual rotation speed when the driven body rotates in the circumferential direction of the annular shape. Claims 1 to 14 are characterized in that the control means does not change the actual movement speed when the actual movement speed is the same or larger than the vibration conversion speed obtained by the vibration conversion means. The control device according to any one of the above items. The vibrating actuator, the control device according to any one of claims 1 to 15, and the like.
A vibration type drive device characterized by having. The vibrating drive device according to claim 16 , further comprising a position sensor that outputs a value representing the relative speed of the vibrating body and the driven body. The vibration type drive device according to claim 16 or 17,
An electronic device comprising a component moved by the vibration type drive device. It is a control method of a vibrating actuator that relatively moves a vibrating body and a driven body.
The case where the vibrating body is vibrated at a predetermined frequency by applying a predetermined driving voltage to the vibrating body, and slip does not occur between the vibrating body and the driven body. Steps to find the vibration conversion speed, which is the moving speed of the driven body,
A step of detecting an actual moving speed, which is an actual moving speed of the driven body when the vibrating body is vibrated at the predetermined frequency, and a step of detecting the actual moving speed.
A control method comprising: a step of reducing the vibration conversion speed when the detected actual movement speed is smaller than the obtained vibration conversion speed.

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